1. Field of the Invention
The subject disclosure relates to ablation catheters, and more particularly, to ablation catheters for performing renal denervation procedures through the renal artery of a patient.
2. Description of Related Art
Renal denervation (RDN) is a procedure performed by interventional radiologists for the purpose of lowering the blood pressure of a patient. Renal denervation is a minimally invasive, endovascular catheter-based procedure using radiofrequency (RF) ablation aimed at treating resistant hypertension.
By applying RF pulses to the renal arteries, the nerves in the vascular wall (adventitia layer) can be denervated. This causes reduction of renal sympathetic afferent and efferent activity which in turn can decrease blood pressure. Early data from international clinical trials demonstrates average blood pressure reduction of approximately 30 mm Hg at three-year follow-ups in patients with treatment-resistant hypertension.
A common way to perform renal ablation is to ablate the renal artery by either heating tissue through radiofrequency or microwave ablation, irrigated heat ablation, and/or cryogenic ablation. It is believed that renal denervation works because it reduces the over-activity of the sympathetic nerve.
Ablation of the renal artery is commonly performed by gaining access through the femoral vein. However, in certain cases, this can cause substantial bleeding. Other options include access through the radial artery. But this method limits the use of catheter systems of 5F (French size) or smaller.
Current ablation catheters that are available to the market include: 1) single polar catheters offered by Medtronic of 710 Medtronic Parkway, Minneapolis, Minn., 55432-5604, which take substantial time to perform effective ablation of the renal artery; 2) cage form catheters offered by St. Jude Medical of One St. Jude Medical Drive, St. Paul, Minn., 55117-9983, which have several electrodes configured in a cage form; and 3) multiple ablation electrodes configured on an inflatable balloon, like those offered by Boston Scientific of One Boston Scientific Place, Natick, Mass., 01760-1537.
All multi-electrode systems have a common disadvantage. They are relatively bulky and large in diameter (7F or larger) and difficult to position into the renal artery, requiring a fixed curve or steerable guiding sheath. The combination of the larger catheter diameter plus the use of a larger guiding catheter often results in an effective system outer diameter of 8F or larger. Such large diameters are not desirable for femoral placement, as it can cause bleeding and result in lengthy recovery periods for the patient.
Another shortcoming of current renal denervation systems is that even though the physician can observe the positioning of the ablation catheter in the renal artery through contrast media supported X-ray, the physician does not know the location of the sympathetic nerves of the renal artery and therefore does not know the correct and ideal position of the catheter to be placed to make the actual ablation and treatment time as short and efficient as possible. Physicians are essentially performing this procedure blind, with presently available devices and the only indication available to a physician to indicate burning of the nerves is the patient exhibiting pain. Even though it is believed that the over-activity of the sympathetic nerves are responsible for higher blood pressure in a patient, the actual place or location of the nerve is not as important as seeing if the patient has an overactive sympathetic nerve signal.
Conventional ablation methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved catheter-based ablation systems. There also remains a need in the art for a system that is easy to make and use. The present disclosure provides a solution for these problems.